Study of Sb2Se3/Al interface affected by oxygen exposure

Antimony selenide (Sb2Se3), a promising low-cost absorber material, is highly attractive in thin film solar cells due to its extraordinary optoelectronic properties. To replace commonly used expensive gold (Au) electrode, the electric properties between Sb2Se3 and aluminum (Al) interface are investigated in detail. We demonstrate that exposure to air generates a Schottky solar cell by formation of the oxides on Sb2Se3 surface and the device performance strongly depends on the oxidation thickness. An optimal PCE of 1.4% is achieved for the first time. X-ray photoelectron spectroscopy (XPS) measurements of the back surface reveal that the oxidation is consisted of amorphous Sb2O3, Se and SeOx. Conversely, the full vacuum device exhibits Ohmic behavior. Moreover, the removal of oxides results in a transition from Schottky to Ohmic contact. Our results indicate that the oxides play a crucial role at Sb2Se3/Al interface, which effects severely the transport of electrons. This study opens up an opportunity for fabricating low-cost high-performance Sb2Se3-based devices with alternative Al back contacts.